Polyazidoformamides



United States Patent 3,526,644 POLYAZIDOFORMAMIDES Shigeto Suzuki, SanFrancisco, Calif., assignor to Chevron Research Company, San Francisco,Calif., a corporation of Delaware No Drawing. Filed Apr. 27, 1967, Ser.No. 634,138 Int. Cl. C07c 117/00; C08f 48/10 US. Cl. 260-349 4 ClaimsABSTRACT OF THE DISCLOSURE Polyazidoformamides of the formula:

in which x is an integer greater than 1 and R is a hydrocarbyl whosevalence is equal to x. Polyazidoformamides of this formula, such ashexamethylene-bis (azidoformamide), are prepared by reacting ahydrocarbyl polyisocyanate with hydrazoic acid. Small amounts of thesepolyazidoformamides are mixed with polyolefins and heated to producenon-crosslinked foamed compositions.

INVENTION BACKGROUND This invention concerns novel polyazidoformamidesand their use as foaming agents in polyolefins.

Polyazido compounds such as polysulfonazides and polyazidoformates havebeen made and used as crosslinking agents for poly-l-alkenes such aspolypropylene. Further, they have been used in conjunction withconventional blowing agents to prepare foamed, cross-linkedpoly-l-alkene compositions.

INVENTION DESCRIPTION In contrast to the previously reported polyazidocompounds a unique group of azides has been discovered which do notcause significant cross-linking but are effective for foamingpolyolefins. These novel azides are polyazidoformamides having thegeneral formula:

wherein x is an integer greater than 1 and R is a polyvalenthydrocarbylgroup of about 1 to about 30, preferably about 2 to 20 carbon atomshaving a valence equal to x in which the valences are on differentcarbon atoms of groups having more than 1 carbon atom. Preferably x isan integer in the range of 2 and 4.

R in the above formula may be alkylene, alkenylene, cycloalkylene,cycloalkenylene, arylene, alkarylene or aralkylene. Examples of typicalgroups are ethylene, isopropylene, tetramethylene, hexamethylene,1,4-hexylene, octamethylene, cyclohexylene, cyclohexenylene, phenylene,tolylene, xylylene, naphthylene, methylenediphenylene,ethylenediphenylene, methinetriphenylene and the like.

Exemplary polyazidoformamides having the above formula are ethylene-bis(azidoformamide), isopropylenebis (azidoformamide), pentamethylene-bis(azidoformamide), 1,3-amplene-bis (azidoforrnamide),1,3-cyclohexylene-bis (azidoformamide), phenylene-bis (azidoformamide),p-tolylene-bis (azidoformamide), mand p-xylylene-bis (azidoformamide),1,3,7-naphthylene-tris (azidoformamide), methylenedi-p-phenylene-bis(azido formamide), and metbinetri-p-phenylene-tris (azidoformamide).

The novel polyazidoformamides of this invention may be prepared byreacting a hydrocarbyl polyisocyanate 3,526,644 Patented Sept. 1, 1970ice with hydrazoic acid. The hydrocarbyl group of the polyisocyanatecorresponds to R in the above formula. The relative proportion of thesereactants is not critical. Normally they will be reacted in amountsapproximating stoichiometric proportions. Preferably a slight excess ofpolyisocyanate will be used. The reactants will conventionally be mixedby dissolving the polyisocyanate in a solution of hydrazoic acid in aninert solvent such as a chloroform, carbon tetrachloride, benzene,xylene and the like. This reaction may be carried out at temperatures inthe range of about 0 to 50 0., preferably at ambient temperature. Itwill normally be complete within 2 to about 72 hours. The crudepolyazidoformamide may be removed from the solvent at temperatures belowthe decomposition temperature of the polyazidoformamide undersubatmospheric pressure. These compounds may be purified by conventionalmethods such as recrystallization.

In general, these polyazidoformamides are colorless crystalline solidswhich decompose or melt with decomposition above about l10 C., usuallyabout 130 to 200 C. Nitrogen is evolved as these compounds decompose.

UTILITY The polyazidoformamides of this invention may be used to preparefoamed solid polyolefin compositions. They may be used for this purposewith solid polyolefins such as polystyrene, polyethylene, stereoregularpolypropylene, poly-l-butene, polyvinylchloride, mixtures of suchpolyolefins and copolymers of polyolefins. Preferably, they will be usedto prepare foamed compositions of stereoregular polypropylene.

Known techniques, which involve blending the polyolefin andpolyazidoformamide and heating the blend to temperatures between thedecomposition temperatures of the polyazidoformamide and the polyolefin,may be used to prepare these compositions. Normally about 0.1 to 10weight percent polyazidoformamide, based on the polyolefin, is blendedwith the polyolefin. Blending may be accomplished by intimately mixingparticulate polyolefin with particulate polyazidoformamide. This mixturewill usually be heated coincidental to extruding or molding the mixtureinto useful objects.

Other components such as dyes, pigments, stabilizers, internallubricants, fillers, etc., may also be blended with the polyolefin ifdesired.

EXAMPLES Example 1 A chloroform solution containing 0.00184 mole per ml.of hydrazoic acid was prepared from sodium azide and sulfuric acid. Inthis preparation a 1-liter flask was charged with 45.5 g. (0.7 mole) ofsodium azide, 45.5 g. of warm water, and 210 ml. of chloroform. Theresulting two-phase system was cooled in an ice acetone bath to about 0C.; then 36 g. (0.35 mole) of sulfuric acid was slowly added whilekeeping the temperature in the range of 010 C. When all of the sulfuricacid had been added, the two phases were separated and the upperchloroform solution was found to contain l.84 10 moles/ml. of HN inchloroform.

200 ml. of the above solution (0.368 mole of HN and 16.8 g. (0.10 mole)of hexamethylene diisocyanate were charged to a flask and allowed tostand at room temperature in the dark for 60 hours. At the end of thistime an infrared spectra of the solution indicated conversion ofisocyanate.

The reaction liquid was mixed with chloroform to give a total volume of700 ml. The small amount of insoluble matter was removed by filtrationand found to weigh 1.7 g. The mother liquor was evaporated to about 100ml. in volume by passing nitrogen over the surface. Upon warming allprecipitated material was redissolved, and upon cooling to roomtemperature colorless crystals formed and were removed by filtration.Other crops of crystals were also obtained to give a total crude yieldof 22.4 g. (88% yield) of hexamethylene-bis (azidoformarnide). Themelting point was 119-120 C. with evolution of small bubbles of gas. Thecrystals had the following analysis:

Calculated for C H N O (percent): C, 37.8; H, 5.5; N, 34.1; 0, 12.6.Found (percent): C, 38.0; H, 5.54; N, 43.87. Infrared analysis gaveabsorption at 3435, 2140, 1700, and 1500 cmf Example 2 A hydrazoic acidsolution was prepared as described in Example 1. This solution contained0.25 mole of HN in 160 ml. of chloroform. This was mixed with 7.52 g.(0.04 mole) of m-xylylene diisocyanate dissolved in ml. of chloroform.This mixture was allowed to stand for about 61 hours in the dark atambient temperatures. At the end of this time an infrared analysisshowed that the reaction was incomplete. Chloroform was stripped fromthe solution by blowing with nitrogen until a concentrated solution wasobtained. Then 150 ml. of chloroform containing 0.26 mole of HN wasadded and the mixture allowed to stand for an additional 54 hours. Theinsoluble, white crystals that formed during this time, 2.09 g., wereremoved by filtration. The mother liquor was evaporated to dryness togive 8.6 g. of residue. Recrystallization of the residue from benzenegave rn-xylylenebis (azidoformamide), having a melting point of 118 122C. dec. The elemental analysis was as follows:

Calculated for C H N O (percent): C, 43.8; H, 3.68; N, 40.9. Found(percent): C, 45.7; H, 3.9; N, 37.0. Infrared analysis gave absorptionbands at 3425, 2151, 1699, and 1499 cm.-

Example 3 A chloroform solution containing 0.25 mole of hydrazoic acidin 150 ml. of chloroform was added to 6.29 g. (0.27 mole) of m-phenylenediisocyanate in a flask. This mixture was allowed to stand for about 15days in the dark at room temperature. At the end of this time aninfrared analysis indicated about 90% conversion of isocyanate groups.The chloroform was removed by passing nitrogen gas over the surface ofthe liquid at C. The residual solid was dissolved in 50 ml. of ethanolwhich was then concentrated to 10 m1. Crystals formed slowly and afterthree days were removed by filtration. In this way 2.1 g. of crudem-phenylene-bis (azidoformamide) was recovered. In melting it started todecompose at about 135 C.; infrared analyses indicated that it wasessentially all azide but that some unreacted isocyanate was alsopresent.

Example 4 A chloroform solution containing 0.24 mole of hydrazoic acidin 160 ml. of total volume was prepared as before. To this was added 7.5g. (0.03 mole) of 4,4-diphenylmethane diisocyanate contained in 150 ml.of dichloromethane. This mixture was stirred for about three days atroom temperature. At the end of this time the solvent was stripped fromthe mixture by evaporation under nitrogen. The resulting crystallineresidue, 8.55 g. (98% yield), was extracted for 16 hours with chloroformto give fine, pale yellow crystals of methylene di-pphenylene-bis(azidoformamide). This compound appeared as a crystalline solid havingno discernible melting pggnt, but it began to decompose upon heatingabove 1 C.

4 Elemental analysis.-Calculated for C H N O (percent): N, 333. Found(percent): N, 31.32. Infrared analysis gave absorptions at 3420, 2148,and 1690 cmf Example 5 43 g. of heptane insoluble polypropylene wasmixed in a Brabender apparatus with 1% of some of the compounds preparedabove. Mixing was continued at elevated temperatures until all of theazidoformamide compound had dissolved. The torque requirements for aconstant mixing speed were measured. The results are given in Table I.

TABLE 1 Torque Compound tested Time Temp. (product of example) (min) F.)Start Finish Polypropylene 8 350-400 2, 500 1, 180 1 s 370-400 2, 5001,080 2 7 370389 3, 700 1, 3 9 378-410 3, 500 1, 310

These results indicate that the compounds of this application causefoaming but not cross-linking of the polypropylene polymer. Afterincorporation of the azidoformamide compounds at these elevatedtemperatures, the polypropylene was a foamed article as indicated by themyriads of fine bubbles throughout the sample. These foamed samples weresoluble in Decalin which also indicates that there is no cross-linkingof the polypropylene.

Example 6 Polyvinyl chloride containing 1 part of dioctyl phthalate and0.03 part of tin stearate in 2 parts of polymer was mixed withrepresentative compounds of this invention and then formed into a foamedproduct by heating at 225 F. for 10 minutes and 360 F. for 15 minutes.The results are given in Table II.

TABLE II Compound tested Wt. percent Foam density (product of example)of compound (grams/cc.)

These results show that the compounds of this invention foam polyvinylchloride to as much as 2 to 4 times its original volume. The thus foamedpolyvinyl chloride samples are soluble in hot dimethyl formamide,indicating that no cross-linking has occurred.

I claim:

1. Compound having the formula t al-..)

No references cited.

JOHN D. RANDOLPH, Primary Examiner C. M. SHURKO, Assistant Examiner US.Cl. X.R. 260-2.5

